Construction board and method of making same



April 24, 1951 E. EGER 2,550,143

CONSTRUCTION BOARD AND METHOD OF MAKING SAME Filed NOV. 29, 1947.ATTRNEY BY mzfmw Patented Apr. 24, r`1.951

CONSTRUCTION BOARD AND METHOD- F MAKING SAME Ernst Eger, Los Angeles,Calif., assgnor to United States Rubber Company, New York, N; Y., `acorporation of New Jersey Application November Z9, 1947, Serial No.788,895

14 Claims. (Cl. 2GB-17.2)

This yinvention relates to a composition of matter in the formV of aboard which is useful for construction purposes and l'to a method ofmaking same.

The principal object 'of the present invention is to :provide animproved board useful for constructional purposes. Another object is toprovide a-method of making such a board. Another object is to provide astructural boardv which is name-resistant even though a large proportionof combustible fibrous material enters into its composition. Anotherobject is to provide such a board which is cheap to manufacture, strong,light in weight, resistant to Water and rmoisture and which may beproduced either in relatively compact form for use as a backing orpaneling material useful either in furniture or in the building trade orin a more porous, softer, less compact formhaving propertiesparticularly adapting it for heat insulation or sound deadening. Anotherobject is to produce a fibrous board of the foregoing type Without usinghigh-pressure equipment. Another` object is to provide a composition andVmethod yielding a brous board without requiring the application ofpositive mechanical pressure during the setting of the mixture. Numerousother objectsfof the present invention will more fully hereinafterappear.

In the accompanying drawing:

Fig. l is a flow diagram of the process of manufacture ofthe board ofthe present invention.

Fig. 2 is an edge view of a relatively compact board made in accordancewith my invention. This view portrays the appearance of a cut edge orcross-section of the board;

Fig. Sis a similar view of a less compact boardv Amade in accordancewith the present invention and especially useful for thermal insulatingand sound absorbing applications.

I have discovered that an improved construction board can .be preparedby intimately mixing a brous material with an aqueous mixture comprisingdispersed polymerizedv chloroprene and dissolved partially condensedvresorcinol-formaldehyde resin, allowing the aqueous mixture to set to afriable solid gel state, and drying to remove the water.

Any fibrous materialmay be employed in making the board of the presentinvention but I prefer to use ibrous material a substantial pro portionof which is composed of bers which are relatively elongated, i. e.,which are long relative to their thickness, and which are adapted tointerlace and form when bonded 'with the binder of the present inventionahomogeneous rboardlike structure of interlaced -bers in randomdistributionexhibiting greatstrength althoughjlight in weight. Inpractice I prefer that atleast 40% of the fibrous material employed beof such randomly interlacing fibers. Such interlacing fibrous materialis to be distinguished from a granular or powdered fibrous material likesawdust, wood our orcork which vdoes not Yin'terlace and which when usedalone does not give a product having the desired great strength. Y

- Examples of interlac'ing'brous materials which are sufficiently cheapand readily available to 'be employed -in making lthe board of myinvention are straw, bagasse, cornstalks, cottonstalks, palmetto liber,jute liber, oat hulls, shredded woodbers such as excelsior, explodedwood fibers,

wood'barkiiber, etc. I prefer to use organic ber which is a by-productof the lumber industry or of agriculture and which vis available at verylow cost and vis obtained chiefly asa waste product. The fibrousmaterial is almost valways organic although I-can use inorganic fibrousmaterials such as asbestos, glass liber, slag, rock or mineral woolyetc.provided they are not too costly.

I have obtained unusually good results by the use of, a mixtureofshredded wood fibers, and

` ground .corkthe wood Iiberconstituting the in-v terlacingber componentof themixture andthe cork serving as a non-interlacing fibrous compofnent which ,lls the voidsbetween the elongated, wood Yibers and giving astrong lyet lightprode uct. I especially prefer to employ a mixture of4wood 'bark ber and wood bark cork both of which are found inthe barks ofevergreens Use of a mixtureconsistingof approximately equal proportionsof such wood bark fiber and such do# mestic cork obtained in knownmanner from 'evergreen bark is :especially satisfactory from -thestandpoints of low cost and ready availability. A

The use of substantial proportions of cork in;` admixture with theinterlacing brous material isv highly.. preferred `because itproduces aboardv which is much lighter in weight ythan a 'similar board in whichno cork is employed. At the" same time the board made with cork hasadequate 'strength and other characteristics adapt' ing/it forstructural uses. The use of cork in the formof native woodrbark cork isespecially advantageous because such cork is much cheaper than theimported cork from the cork oak. I prefer' to use cork in `amountranging from 40 to of the fibrous material employed.

In practicing the present invention the fibrous material `is-int-imatelymixed with an aqueous mixture comprising dispersed polymerizedchloroprene and dissolved partially condensed resorcino1-formaldehyderesin and containing a condensing agent capable of effecting furthercondensation of the resin from the water-soluble state to asubstantially insoluble substantially infusible state. After-effectinguniform intermixture of the brous material and the aqueous binder, themixture is shaped to board-like form, as by troweling into place or inany other suitable manner. The resulting mixture is then allowed tostand, taking precautions if necessary to insure that substantialevaporation from the interior of the mass does not occur until theaqueous binding mixture sets to a friable solid gel state. After gellinghas taken place, the board-shaped material is dried to remove the water.The drying step completes the resinforming reaction, carrying the resinto the insoluble infusible stage and effects removal of both ywater ofreaction and water of solution, forming a tough, strong, flexiblebinder.

It is important that the shaped mixture be heldimmobilized, i. e. withits various parts stationary with respect to one another, during thegelling and during at least the major portion of the drying. Otherwise a-satisfactory bond is not obtained. Preferably the material islmaintained in undisturbed condition until at least 90% of the waterpresent has been removed.

In some. cases the brous material may be wetted with water beforeintermixing it with the aqueous binding composition. This pre-wetting ofthe fibrous material causes it to mix more easily and more uniformlywith the aqueous binding composition. Preferably the ber and theprewetting water are intimately mixed together in any suitable mannerprior to addition Vof the binding composition. Where a mixture offibrous materials, such as the mixture of wood bark ber and domesticcork described above, is employed this preliminary mixing with thepre-wetting waterhas the additional advantage of vfacilitatingintermixture of the various types of fibrous material with one anotherso that a, better and more uniform product is obtained. The amount ofwater employed to pre-wet the fibrous material in the manner justdescribed may vary widely depending upon `many factors including thewater-absorptivity of the fibrous material; itl may range from-fonly asmall amount up to that required to completely saturate the fibrousmaterial. Usually the pre-wetting water is employed in an amount equalto at least 5% Aby weight of the fibrous'material.

Instead of pre-wetting the fiber with water as just described, it isvoften more advantageous and practical to add the water for wetting thefiber to the aqueous binding composition, water` being added Ythereto inamount sufficient to dilute it substantially below 30%Y and usually tonot over 25% of elastomer plus partially condensed resin, the dilution,however', being only to such anv extent that the elastomer plus resincontent of the aqueous binder vleft after absorption of water therefromby the fiber is at least 30%. For example the fiber-wetting water may beadded to the aqueous binder and the fiber then added to the resultingdiluted binder with mixing whereupon the fiber absorbs the excess waterrapidly. This mode of operation is preferred since it has the advantageof eliminating one mixing operation, namely the pre-wetting-operation,the abs orption of the excess water by the fiber aiding in the mixingand readily giving a mixture which can be troweled into place orotherwise shaped for the production of the board.

Alternatively, a portion of the added water may be used to pre-wet theber and the rest may be employed to dilute the aqueous binder.

An important requirement in practicing the present invention is that theWater content of the mixture be so adjusted that the content of neoprene(polymerized chloroprene) plus partially condensedresorcinol-formaldehyde resin in the aqueous mixture present on andaround the bers after intermixture be at least by weight of such aqueousmixture. For example, if the fibrous material is completely saturatedwith water in the preliminary wetting step described above, the aqueousbinder admixed there- A with should contain at least 30% of neopreneplus resin. If on' the other hand the fibers are dry or are incompletelysaturated with water, then the aqueous binder commingled therewith canbe diluted with water to a neoprene plus resin content below 30%provided the fibrous material is capable of absorbing enough water fromthe aqueous binder to raise the neoprene plus c resin content thereof atleast to the 30% level.

Unless the neoprene plus resin content of the aqueous binder in themixture after intermixture of fibrous material and binder is at least30%, the binder will not go through the solid friable gel state and asatisfactory bond will not be obtained.

The aqueous binder composition should contain neoprene and the partiallycondensed resin in such relative proportions that the resorcinol contentof the resin ranges from 3.8 to 16.8 and preferably from 6.75 to 15.0per cent by weight based on the Vweight of neoprene. Unless these limitsare observed, the material obtained byv gelling and drying of thebinding composition is not satisfactory as a binder for the fibrousmaterial.

The speed with which the binding composition used in the presentinvention gels to the requisite solid friable gel state isgreatlyaffected by the temperature, increasing rapidly therewith. Thus at roomtemperature it may not gel for several hours but as the temperaturerises above F. it begins to gel very rapidly and at F. it gels almostimmediately. For this reason, gelling may be greatly accelerated bysubjecting the shaped mixture to elevated temperature conditions.

The speed of gelling is also greatly affected by the concentration ofneoprene plus partially condensed resin in the aqueous binding mixturesurrounding the fibers after mixture has been effected. Increase of thisconcentration by a few or even by a single per cent effects aconsiderable shortening of the gelling time. This concentration is oftenat least 35% and it may range as high as 55 or 460 per cent.

For this reason gelling is greatly accelerated by the phenomenon ofabsorption of water from the binding composition by the fibrous materialwith which it is mixed. If the fibrous material mixed with the aqueousbinding composition is dry or is incompletely saturated with water, itwill selectively remove water from the binding composition and therebyconcentrate the same so that it will gel or will gel more rapidly.

After intermixture of the fibrous material with the aqueous bindingcomposition and shaping thereof to the desired board-like form,evaporation of volatile material, principally water, from the mixtureshould be so limited that the requisite gelling takes place before anysubstantial surface evaporation occurs. '-If :surface evaporapreferablyatelevated temperature to acceleratev gelling, for example by*maintaining same in a heated atmosphere of controlled high humidityuntil gelling has taken place. After gelling has been effected, theresulting mixture maybe `dried inanysuitable manner. I prefer` toyemploy elevated temperature during the dryinglstep to accelerate thesame. For example l may employ a temperature fof from 1259-1?. to 150 F.in the drying step.

1. Il` often prefer to place. the Wet mixture of fibrous material andbinder in sheet .form betweenscreens or perforated ysurfaces which maybe free `tomove `or' may be locked in any suitable manner to Vprevent.separation during setting, the

gelling and drying steps being carried out whilev thefmaterial isbetween such screens or the like.

It is important that `the wet shaped; mixture be maintained in arelatively undisturbed condition until `it has taken its set, i. e.immobilized during the. gelling step .and during the major portion ofthe drying step, i. eruntil substantially all the. water-has beenremoved. The material is usually dried until at least 90% by weight ofthe water present has been removed before itis subjected to forces whichwouldtend to disturb the relative positions of Ythe various portionsthereof. If the material is' disturbed before it has taken itsfinal set,i. e. before the major rportion ofthe Water has been removed, it will bedisintegrated into discrete portions. and rendered worthless.

The aqueous composition `used to form the binder in accordance with myinvention is preferably ycomposed essentially Vof an aqueous `mixtureAof dispersed polymerized chlo-roprene, .clis-v solved partiallycondensed Water-*soluble resorcinol-formaldehyde resin :capable ofsettingupon removal of water by `further condensation to a substantiallyinfusible, Asubstantially insoluble state, and an alkali metal hydroxidecapable; of effecting such further condensation ofjsaid resin. Thislcomposition is most conveniently prepared by simply mixing an aqueousdispersion of polymerized chloroprene with an aqueous solution of thepartially condensed resorcinol-formaldehyde. l

resin `and an aqueous solution of alkali metal hydroxide. The aqueousmixture may embody otheningredients such as suitable proportions offillers, pigments, anti-oxidants, dyestuffs, suspending agents,dispersing agents, wetting agents, etc. such asagents for holding thepolymerized chloroprene and the llers or pigments in suspension in theaqueous medium. The aqueous mixture may contain ingredients solubilizingor holding in solution the partially condensed resorcinol-formald-ehyderesin, a preferred example of such a material being an alkali metalhydroxide, typically sodium hydroxide. The lcomposition will containexcess or unreacted formaldehyde for completing condensation of theresin and effecting hardening'such other components of the formulationas casein, glue, etc. It is preferred that the aqueous compositionembody. a catalyst for effecting completion of the resin-formingcondensation, such catalyst preferablybeing an excess of alkali metalhydroxideV i in formulating 'the resin may vary Widely but usually amolar excess of formaldehyde over res-` orcinol is employed to give theultimate formation of an insoluble infusible resin. The resorcinol andformaldehyde are preliminarily reacted together, the reaction beingstopped before completion, i. e. before lthe condensation product hasreached the insoluble infusible stage which may also be before all theformaldehyde has reacted. The ,partially condensed resin is soluble inWater andy in dilute .aqueous alkali metal hydroxide-solution. Ifdesired the resorcinolmay be reacted withy a .part only .of theformaldehyde and the remainder of the formaldehyde may be added to theformulation at any time prior to use.

In themanufacture of the partially condensed resin capable of settingupon removal of Water to the insoluble infusible stage, it is oftenpre-` ferred -to employ a molar ratio of total formaldehyde toresorcinol ranging from V2:1 to l3:1.

Upon gelling and drying, :the incomplete kresinforming reaction proceedsto completion. The free formaldehyde present after the initial reactionis available to carry the reaction to completion during the drying stepand also to harden :and insolubilize any protein such Aas casein-.or

glue present in the -formulation. The preliminary' resin-formingreaction may conveniently becarriedout by forming amixture ofresorcinol` and waterat an elevated temperature, say 130 to 200 F., andadding the formaldehyde, e. g. in the form of commercial 37 to 40%aqueous solution, withstirring. It may be desirable to add the formal-idehyde-gradually over a considerable period of time in View of thehighly exothermic nature Vof the .resin-forming reaction which, ifallowed to get out of control, may yield a completely unusable resin.`If desired, known catalysts vfor the resin-forming reaction such asoxalic acid, ben-v zene sulfonic acid, etc. may be employed. Preferably:ho-Wever an alkali metal hydroxide, typically included inthe finalvcomposition additional aqueous alkali metal hydroxide solution beyondthat necessary vto hold the partiallycondensed` resin in' solution, suchadditional alkali metalhydroxide serving to complete the resin-formingreaction las above stated. The resulting mixture `is unstable, that is,it gels upon standing for a relatively short time, usually not over 8hours, the length of'` time required -for gelling to take placedepending upon many factors, especially the 'concentration Yofneofpreneplus resin and thertemperature to which the mixture is subjected.

Any "desired .proportions 'of.1; igments,I llers, etc.

may be used in the formulation depending uponv the desired consistencyof the aqueous mixture and the properties desired in the final gelled`and dried binder. The proportions of casein or similar protein willusually not exceed The proportion of alkali metal hydroxide present inthe nal formulation will not ordinarily exceed 2% but is'usually atleast 0.1% of the aqueous mixture used to form the binder. Thesepercentages are by weight of the total binding composition on awater-free basis.

When, as in the preferred practice of my invention, polymerizedchloroprene is the sole rubbery or elastomeric material present, thegelling and setting of the aqueous mixture does not depend uponvulcanization and in fact no vulcanizing agents, accelerators or thelike ingredients are used in the aqueous mixture. The excellent resultsof the present invention are obtained Without'vulcanization merely byallowing such an aqueous composition to gell followed by drying toremove the water.

Where reference is made herein to the proportion of partially condensedresin (as where I refer to thev percentage of the sum of polymerizedchloroprene and resin), the sum of resorcinol and the total formaldehyderequired to set the same to the insoluble infusible state is intended,although all such formaldehyde is not combined in the initialresin-forming condensation. Of course formaldehyde in excess of suchrequirement is not included although the amount of such excess wouldordinarily be so small as to be almost inconsequential.

Instead of using an aqueous dispersion of polymerized chloroprene(neoprene) in the practice of my invention I may less preferably uselatices ofelastic rubbery or rubber-like sulfur-vulcanizablematerialssuch as GR-S (butadiene-styrene synthetic rubber) latex, Buna N(butadieneacrylonitrile synthetic rubber) latex, isoprenestyrenesynthetic rubber latex, etc. in the same proportions as given above forneoprene latex. I may also use blends of such other rubbery materials inlatex form with neoprene latex. However when latices of rubbery materialother than neoprene are used it is necessary to include the conventionalvulcanizing ingredients in the composition and to cure at a temperaturesufficiently elevated; to effect vulcanization of such other elastomericmaterial. Such temperatures are considerably above those required whenneoprene is used as the sole rubbery component of the formulation` Asexplained above simple drying of the neoprene formulations attemperatures only sufficiently elevated to effect removal of the Wateris all that is required. Neoprene gives a much better product than theother rubbery materials. When a neoprene latex by itself is airdried itgives a tacky film but the combination with the resorcinol-formaldehyderesin as described herein gives upon air-drying a tack-free lm; withlatices of other elastomers such as GR-S this reduction of tackiness bythe resin is not nearly so pronounced. For these and other reasons,neoprene is by far the preferred elastomer. Y

While I much prefer to use resorcinol in the practice of my invention, Imay use equivalent proportions of pyrogallol which gives a resinformingVreaction substantially the same as that described above for resorcinol.Resorcinol and pyrogallol are similar, both being polyhydric phenolshaving hydroxyl groups in the 1- and 3,-positions on the benzene ring,pyrogallol differcomposition which when shaped, allowed to go' ing fromresorcinol in having the 2-position also occupied by hydroxyl.

Instead of pure resorcinol, I may with substantially equivalent resultsuse commercial resorcinol which contains related phenolic bodies asimpurities and usually contains at least of resorcinol.

Instead of formaldehyde I may use equivalent proportions of otherwater-soluble aldehydes capable of giving the resin-forming reactionWith resorcinol or pyrogallol. Examples are other aliphatic aldehydessuch as acetaldehyde, propionaldehyde, butyraldehyde, etc. I may evenuse furfural although when it is used I prefer to use it only in makingthe partially condensed water-soluble resin and to use an aliphaticaldehyde such as formaldehyde or a homolog thereof in the formulation tocomplete the resin-forming reaction. I may use one aliphatic aldehyde inthe initial resin-forming reaction and use another in the formulation tocarry this reaction to completion; thus I may employ formaldehyde inmaking the partially condensed resin and then a homolog such asacetaldehyde or propionaldehyde to complete the reaction; oracetaldehyde first and then formaldehyde to complete the reaction; orpropionaldehyde first and then formaldehyde or acetaldehyde.

I prefer to use resorcinol in conjunction with formaldehyde both for thepartial condensation and to complete the resin-forming reaction or inconjunction with furfural for the initial condensation and formaldehydeto complete the condensation.

The mixture of the fibrous material and the aqueous binding mixture mustbe given its nal shape prior to the occurrence of gelling becausematerial shaped from the mixture aft'er gelling has begun or iscompleted will not have enough strength to be useful.

The relative proportions of fibrous material and aqueous bindingcomposition employed in manufacturing a fibrous board in accordance withmy invention may vary widely depending upon many factors includingphysical characteristics desired in the board, type of fibrous materialused, etc. The amount of binder should be sufficient to produce astrong, coherent board capable of standing up during handling,installation and use. I have successfully used the binding compositionin a proportion such that the amount of elastomer plus partiallycondensed resin ranges from 20 to 70 parts by weight per parts of thebrous material such as wood fiber and ground cork. Use of from 20 to 40parts of elastomer plus resin per 100 parts of wood fiber and groundcork gives a mixture which can be troweled and thus easily shaped intothe desired board-like form.

I have found that formulation of a mixture consisting of approximatelyequal parts of wood bark fiber and ground wood bark cork and an aqueouselastomer-partially condensed resin binding composition in relativeproportions corresponding to from 20 to 40 parts of elastomer plus resinper 100 parts of the fibrous material, the relative proportions ofelastomer and resin being such that the polyhydric phenol content of theresin ranges from 3.8 to 16.8 per cent by weight based on the Weight ofelastomer and the concentration of elastomer plus resin in the aqueousmixture surrounding the fibrous material following intermixture being atleast 30 per cent by weight of said aqueous mixture, gives a 9 throughthe: gell stage and dried; yields ea-A compact boardV which lendsitselfas a backing mate'- 'ral or panelingl `material and. can beiLutilized in furniture orain the building trade. I: believe that thegreat shrinkage 'of the-aqueous binding l material, A when it is-Aemployed iny such proportions, effects compaction `ofA the fibrousmaterial during the drying step. Ihave observed that there is about l to11% llinearshrinkage'of the mixture during drying and that this shrinleage compacts -the ber; Thislgreatshrinkage enablesme to obtain a compactboardwitho-ut'the necessity of using expensive highpressdreplatenpresses. Thus I can simply place the wet intermixture of brous materialand binder between 'screensor like perforated surfaces allowing escapeof `water and hold it there'untiigeilingand drying are accomplished Inmaking sueh-k -a hard, compact board, it is desirabley to leave the top.and bottom ofthe form asI -Wel1- as `the sides f free so as to enablethese to follow'the shrinkage ofthe-materialtv v The techniquedeseribedvin '-thepreced'ing-par graph requires only 4very simple and#inexpensive Lequipment' Vandthe application of vno positive externalmechanical". pressure. Although' the shrinkage upon gel/ling and dryingofA the f aqueous.) neoprene-partially condensedi--resorcinolformaldehyde composition byy itselfL .or with the ordinaryfillers andpigments but withouteinter- `mixture of alarge-proportion ofnbrousmaterial is? often so excessive -as toprecludes--the vproductiontherefromuof useful articles-thicker than one-fourth of an inch,nevertheless-the present inventiontakes advantage of4 this greatshrinkage to; obtain an. unexpected resulti namely '-the production i ofa-= compacting action-- whicha eliminates the; lneed of i highpressure`equipment :and yields a useful product even when made in Agreatthickness'say upto three-fourthsofan inch. orleven greater. Infotherwords rshrinkage impcsesrno limitation on thickness of the`boardproduceelaby my invention, Atheonly limitations oni-:thickness ofmy. board-s being-thatimposedfby-the=dif`u`culty of drying. extremelythickf boards.- Fora thin boa-rdi the particle 'size` of theJ ber'Ilimits `the -thinness -ofithe board'. f

I havevfurther fou-ndi that by: incorporation` of ya minorfproportionfcottonor rayon l fiber: into the.y composition .dl-ascribed abovegV a`much-less compact board'isobtainedi Thisembodiment of my invention isespecially-valuable where aboard having Va rather. lou/weight`per-square foot characteristic .and a ratherwpcrous: and loosely`connectedistructurefor the purposeof sounctdead ening and temperatureinsulation'isdesired.` For this` purposeI may incorporate .intothesformulation from 5 i tor 20% by weight based: onL the weight of.other fibrous material, such asamixture of wood ber and cork, of groundwasteicellulosefbers, preferably the vfibersA thatffarereclaimed fromold tire carcasses madeffrom cotton or..rayon .byY vcrackingror grindingtiresito'- about to. .1@ inch `particle size, then passing this groundmaterial through-avmechanical device that' .beats` the. liber free fromrthe rub-ber: and separates it; by air suction. Suchnb-ers mayfbedescribed.I as Acotton and/or` viscose. rayonfiber i' composed of avmixture of twisted :cordand shredded.` singlet strands both'spunandilunspun r i in.various1.lengths, the ber length=varyin`g from1/4' to.l inch Vwith' the .bulk around .1/4` inch. The use; of such; a..minorinproportionI` of short-l'ength (lengthrgenerally averaging il@ of:anrinc-h) cel-.- lulose.` textile; f. bers produces .unusual results;

yielding amore-porous; muchfless com-pactboard than the same composition1from-which ^such fibers are omitted. Atithei same time the lighterboard so obtained has suicient strength and other'c-haracteristicsadapting itv to use-as aicon- `s tructional material: The resultingboard -canbe laminatedvvith various materialsV sucl'ras` a resinoussheetorproducing awall-v panel that can be; directlyapplied tothe studding ofa building and" become 'parir of the building. Thisboard, like the vmorecompact-i board obtainedV without the' cotton or rayon;is-flameresistanhInstead ofreclaimed tire-cord; *I may use cotton orl rayon-'nook' or'any ot-her/form-'ofV shortlength- L substantially pure-cellulose ber,such *as cottonor;regeneratedf'cellulose textilefiberruniformly'dist-ri-buted throughout "the mixturel from whichtheboardr-ismade;4 However' from the standpoint' of cheapness- I prefer touse the waste tire fabric.` f

I am not'certainas to -hoW the intermixture ofthe minor proportion ofcotton'or raycnfiber bringsabout the fresultdescribed. 'l Neverthelesssuch intermiXture-results in a substantialidimins "ishing'oi thecompactingeifeot ofthe binder Without preventing formation of a lstrong,useful board; It may be that the cotton or rayon bers have a tendency tofilter out vthe elastomersand resin constituents of the aqueous mixtureand thus prevent the penetration thereof into. the wood ber andcork'v sothat"afte`r dryingtlie resulting assembly `is intenocked" through.; faceadhesion `of coated cotton or rayon fibers with th'W'ood fiber and cork`but due tothe lack of binder adjacent the latter sufficient voids areleft therebetween to give a softer and more porous materiallendingitself `touse as ai'heat insulating and sound absorbing material? It maybe that the cotton'-or'frayon ber, being substantiallyi pure cellulosehighly swellabiei by aqueous-f4 media is highly` ,swollen shy, theaqueous mixture and upon .dryingshrinks back to itsoriginalsizaleavingvoids and holding su'cient- 1y someof the 'wood bersapart preventing .the binder from contracting upon drying, thus'.forming a porous board. Thealkali,metalhydroxide condensing agent in ,thebinding` Vmaterialyifoillcl accentuate such swelling. "Iheotherfibers..pres-` ent SuchasWoQdJber 'andccorlaA being:- very impure, Woodyligninfcontaining cellulose which is relatively nonfswellable by aqueousmediasas compared to pure cellulose such as cottonpand rayon, would' not*undergo suchH great swelling and subsequent shrinkage leaving voids;V'In the preferred practice of my inventionno positive externalmechanical. pressure'is applied to the shapedmixture during the gellingyand drying steps, sole reliance. being placed uponthe self-compactingYnature of" the mixturetoieifect the production ofthe desired boardhaving excellent strength and others physical properties adapting; ivtto. structural uses and having the desired degreeofcompactness. l,

I n the accompanying ,dravvingvvhich is largely self-explanatory, Fig.1, is a flow diagram of the process of making the board, Fig. 2 portraysa compact boardmadeasdescribed inzyEXample 1 belowsands Fig...3.1:xortraysY a relatively porous board made iii-.identcali. manner=.ton `\the=board of Fig. 2fexept with.the-incorporationof 102%L-#byweight` ofground. cellulose textile fiber obtained from reclaimed tirecarcasses as described-lin Example'2wbelow. The looser, more poroustexturelofth'e lboard as a result of the intermixture :11 of the cottonor rayon bers will be apparent from inspection of Fig. 3.

EXAMPLE 1 To approximately equal parts of wood fiber and of grounddomestic cork, both derived from vthe bark of native evergreens, wasadded about by weight thereof of water and the materials -were mixeduntil a uniform mixture was obtained. There was then added an aqueousmix- Lture freshly made as described below. The relative proportionswere such that for each 100 parts .of wood fiber and cork there wasemployed 100 parts of said aqueous mixture. Since the aqueouswmixture.contained 28.2% neoprene and 5.05% Yof resorcinol-formaldehyde resin,there were employed 33.25 parts of neoprene plus resin per .100 parts ofthe fibrous material. The resulting materials were mixed to a uniformcondition and the mixture which had a troweling consistency was placedin sheet form between screens, allowed to stand for minutes and thendried at 12S-150 F. A strong, compact ibrousboard illustrated in Fig. 2was obtained.

' The aqueous compositionused to' form the binder was prepared from fourseparate recipes, identified as A, B, C and D which were admixedtogether, just prior to use, in the following proportions by weight.

'Parts by weight Recipe A t 200 Recipe B 40 Recipe C 6 Recipe D 110Recipes A, B, C and D had the following compositions: v

Recipe A This was an aqueous neoprene latex containing 75; vof dispersedpolymerized chloropene.

Recipe B Per cent 'by weight Zinc oxide 12.50 Casein 1.25 Conc.NH4OH(29.4% NH3) 1.25 -Phenyl beta naphthylarnine v 5.00 Lithopone 30.00Sodium salt of short chain alkyl naphthalene sulfonic acid 1.25 Water48.75

, Recipe B was prepared as follows: The casein 'and ammonia were addedto 20 parts of water. The mixture was ball-milled one hour. There-Vmaining ingredients were then" added and the mixture ball-milled for aminimum of 8 hours. The resulting dispersion was stored in such a way asto permit agitation suiiicient to prevent Crushed ice 188 A lbs;

441 ibs. '1oA oz.

12 Recipe D was prepared as follows: 'The resorcinol was placed in thewater which was at a .temperature of approximately 150 F. After mix-EXAMPLE 2 Example 1 was duplicated exactly except that there wasincluded with the wood bark fiber and ground cork 10% by weight thereofof ground cotton and viscose rayon cellulose fiber obtained from tirecarcasses in the rubber reclaiming operation. The resulting board hadthe looser, more porous structure indicated in Fig. 3 of the drawing andwas eminently suited for sound absorption and thermal insulation use.

From the foregoing, many advantages of the present invention will beapparent to those skilled in the art. The principal advantage is that aname-resistant building board having good strength is produced in asimple and economical manner. Another advantage is that the mixture isself-compacting during setting so that a compact board in the case wherethe cotton or rayon liber is not used and a somewhat less compact board,though still sufficiently compact for the purposes required where `suchcellulose fiber is used, are obtained While subjecting the mixture tosubstantially no external pressure during its formation, i. e. aftershaping and during the gelling and drying steps. 'This elimination ofthe necessity of subjecting the mixture to external mechanical pressurewhile it is taking its set is highly advantageous because themanufacture is thereby greatly simplied and accelerated and theequipment investment is much lower since mere placement of the sheetedmaterial between foraminous surfaces such as screens is all that isrequired in contrast to the complexity and expense of using highpressure platen presses. Another advantage of the present invention isthat the mixing of the aqueous binder mixture with the fibrous materialto obtain a uniform homogeneous mixture is greatly facilitated by theform of the aqueous mixture used to form the binder, in comparison toprior art methods of making wall-board or the like using a powderedbinder which is extremely dicult to distribute uniformly around eachfiber and throughout the fibrous mass. Numerous other advantages of myinvention will be obvious from the foregoing description.

All parts and percentages referred to herein are by weight.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A fibrous board comprising a mass of fibrous material comprisingrandomly interlaced fibers bonded together by a bonding mediumcomprising the dried gelled residue of an aqueous mixture comprisingdispersed polymerized chloroprene and dissolved partially condensedresorcinolformaldehyde resin capable of setting upon removal of water toa substantially infusible, substantially insoluble state, said mixturecontaining said polymerized chloroprene and said resin in such relativeproportions that the resorcinol conassortis by weight basedV on theweightof said. polymerized chloroprene andcontaining at least 30 percent by `weight of said polymerized chloroprene and said resin.

2. A fibrous board .composed essentially of a mass of shredded woodliber and ground cork bonded together vby a bonding. medium compris,-

ing the dried gelled residue of an aqueousmixture comprising dispersedpolymerized. `chloroprene and. dissolved partially .condensedresorcinolformaldehyde resin capableV of setting uponremoval of water toa substantially infusible.. sub.- stantially insoluble. state, saidymixture containing. said polymerized ,chloropreneand saidresin in suchrelative proportionsthat the resorcinol content of said resin rangesfrom3.8.to 16.8 per cent by weightbased. onthe. weight of, saidpolymerized chloropreneand containing at. least. 3) per cent by weightvofv said polymerized chloroprene andsaid resinthe weight` vof' saidpolymerized chloroprene and said resin rangingfrom 20.to 70 parts per10Q partsof said woodber and. ground cork.

3. A brous board comprising a massY of fibrous material 'comprisingshredded wood ber and ground cork having uniformly distributedtherethrough a minorproportion of short-length cellulose textile iber,said brous material being bonded together by a bonding medium compris-Ving the dried gelled residue of. an aqueous mixture comprisingdispersed polymerized chloroprene and dissolved partially condensedresorcinol-formaldehyde resin capable of setting upon removal of waterto a substantially infusible, substantially insoluble state, saidmixture containing said polymerized chloroprene and said resin in suchrelative proportions that the resorcinol content ofsaid resin rangesfrom 3.8 to 16.8 per cent by. weight based on the weight of saidpolymerized chloroprene and containing at least 30 per cent by weight ofsaid polymerized chloroprene and said resin, the, weight of saidpolymerized chloroprene and said resin in said composition ranging from20 to 70 parts per 100 parts of said wood liber and ground cork, saidboard being substantially more porous, less compact and less dense thanthe same board from which said short-length cellulose textile fiber isomitted.

4. Aprocess of making a fibrous board comprising intimately mixing amass of fibrous material comprising randomly interlaced fibers with anaqueous mixture comprising dispersed polymerized chloroprene anddissolved partially condensed resorcinol-formaldehyde resin capable ofsetting upon removal of water to a substantially infusible,substantially insoluble state, said mixture containing said polymerizedchloroprene and said resin in such relative proportions that theresorcinol content of said resin ranges from 3.8 to 16.8 per cent byweight based on the weight of said polymerized chloroprene, said aqueousmixture containing after said mixing has been accomplished at least 30per cent by weight of said polymerized chloroprene and said resin,shaping the resulting mixture to board-like form, allowing the shapedmixture to stand until 4said aqueous mixture has set to a friable solidgel state, and drying the resulting mixture to remove the water.

5. The process of claim 4 wherein said fibrous material is wetted withwater prior to completion of admixture with said aqueous mixture.

6, A process of making a fibrous board comprising intimately .mixingy a.mass of shredded wood fiber and ground cork with an'aqueous mix;-

ture comprising dispersed polymerized chloroprene and dissolved`partially condensed resorcinol-,iormaldehyde resin-,capable ofsettingupon removal of water to a substantially infusible, substantiallyinsolubleA state, said mixture contain: ing4 said polymerizedchloroprene-.and said..` resin in such relative proportions that theresorcinol content of said resin ranges from 3.8 to 16.8 per cent. byweight based on the. weight. of said polymerized chloroprene, saidaqueous mixture containing after said mixing has been accomplished atleast 30 per cent by weightof said polymerized chloroprene and saidresin, the weight of said polymerized chloroprene and said resin rangingfrom 20 to 70 parts per 100 parts of said wood fiber and ground cork,shaping the resulting mixture to board-like form, allowing the shapedmix.- ture to stand until said aqueous mixture has set to a friablesolid gel state, and drying the resulting mixture to remove the water.

7; The process of claim 6 wherein said fibrous material is wetted withwater prior to completion ofr admixture with said aqueous mixture.

8. The process of claim 6 wherein said mixture is subjected tosubstantially no external pressure during said gelling and drying stepsand the mix.-v ture is. compacted throughv the sole agency of shrinkagewhich occurs during said drying.

9. A process of making a brousboard comprising forming an intimateuniform mixture of a fibrous material comprising a mass of shreddedwood'ber and ground cork and a minor proportion of short-lengthcellulose textile fiber with an aqueous mixture comprising dispersedpolymerized` chloroprene and dissolved partially condensedresorcinol-formaldehyde resin capable of setting upon removal of waterto a substantially infusible, substantially insoluble state, saidmixture containing said polymerized chloroprene and said resin in suchrelative proportions that theresorcinol content of saidresin ranges from3.8 to 16,8 per cent by weight based on the weight of said polymerizedchloroprene, said `aqueous mixture containing after said mixing has beenaccomplished at least 30 per cent by weight of said polymerizedchloroprene and said resin, the weight of said polymerized chloropreneand said resin ranging from 20r to 70 parts per 100 parts of said WoodberV and ground cork, shaping the resulting mixture to board-like form,allowing the shaped mixture to stand until said aqueous mixture has setto a friable solid gel state, and drying the resulting mixture to removethe water and yield a board which is substantially less compact than thesame board from which said cellulose ber is omitted.

10. The process of claim 9 wherein said brous material is wetted withwater prior to completion of admixture with said aqueous mixture.

11. The process of claim 9 wherein saidmixture is subjected tosubstantially no external pressure during said gelling and drying stepsand the mixture is compacted through the sole agency of shrinkage whichoccurs during said drying.

12. A process of making a fibrous board comprising intimately mixing amass of water,- absorbent brous material comprising randomly interlacedfibers with an aqueous mixture comprising dispersed polymerizedchloroprene and dissolved partially condensed resorcinol-formaldehyderesin capable of setting upon removal of water to a substantiallyinfusible, substantially insoluble state, said mixture containing saidpolymerized chloroprene and said'resin in Ysuch relative proportionsthat the resoicinol content of said resin ranges from 3.8 to 16.8 percent by weight based on the weight of said polymerized chloroprene, saidaqueous mixture containing not over 25% by weight of saidpolymerizedchloroprene and said resin, causing said fibrous material to absorbsuiiicient water from said aqueous mixture during said mixing step thatthe aqueous mixture present on and around the bers after intermixturecontains at least 30 per cent by weight of said polymerized chloropreneand said resin, shaping the resulting mixture to board-like form,allowing the shaped mixture to stand until said aqueous mixture has setto a friable solid gel state, and drying the resulting mixture to removethe water.

13. A fibrous board comprising a mass of randomly and initially looselyinterlaced nbers bonded firmly together by a bonding medium comprisingthe dried gelled residue of a hardenable aqueous mixture comprisingdispersed elastic rubbery composition selected from the group consistingof rubbery copolymer of butadiene and styrene in admixture withvulcanizing ingredients, rubbery copolymer of butadiene andacrylonitrile in admixture with vulcanizing ingredients, rubberycopolymer of isoprene and styrene in admixture with vulcanizingingredients, and rubbery polymerized chloroprene, and dissolvedpartially condensed resin obtained by the partial condensation of apolyhydric phenol having hydroxyl groups in the 1- and 3-positions andan aldehyde and capable of setting in the aqueous condition to a friablesolid gel and capable of being converted upon removal of water to asubstantially infusible, substantially insoluble state, said mixturecontaining said rubbery polymer and said resin in such relativeproportions that the polyhydric phenol content of said resin ranges from3.8 to 16.8% by weight based on the weight of said rubbery polymer andcontaining at least 30% by weight of said rubbery polymer and saidresin.

14. The process of making a fibrous board comprising intimately mixing amass of randomly loosely interlaced fibers with an aqueous mixturecomprising dispersed elastic rubbery composition selected from the groupconsisting of rubbery copolymer of butadiene and styrene in admixturewith vulcanizing ingredients, rubbery copolymer of butadiene andacrylonitrile in admixture with vulcanizing ingredients, rubberycopolymer of isoprene and styrene in admixture with vulcanizingingredients, and rubbery polymerized chloroprene, and dissolvedpartially condensed resin obtained by the partial condensation of apolyhydric phenol having hydroxyl groups in the 1- and 3-positions withan aldehyde and capable of setting in the aqueous condition to a friablesolid gel and capable of being converted upon removal of water to asubstantially infusible, substantially insoluble state, said mixturecontaining said rubbery polymer and said resin in such relativeproportions that the polyhydric phenol content of said resin rangesYfrom 3.8 to 16.8 per cent by weight based on the weight of saidVrubbery polymer, said aqueous mixture containing after said mixing hasbeen accomplished at least 30% by weight of said rubbery polymer andsaid resin, shaping the resulting mixture to board-like form, allowingthe shaped mixture to stand until said aqueous mixture has set to airiable solid gel state, and thereafter drying the resulting gelledmixture and converting the same to a substantially infusible,substantially insoluble state.

ERNST EGER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,398,146 Novotny et al Nov. 22,1921 2,087,942 West July 27, 1937 2,277,941 Almy Mar. 31, 1942 2,314,998Lessig et a1 Mar. 30, 1943

13. A FIBROUS BOARD COMPRISING A MASS OF RANDOMLY AND INITIALLY LOOSELYINTERLACED FIBERS BONDED FIRMLY TOGETHER BY A BONDING MEDIUM COMPRISINGTHE DRIED GELLED RESIDUE OF A HARDENABLE AQUEOUS MIXTURE COMPRISINGDISPERSED ELASTIC RUBBERY COMPOSITION SELECTION FROM THE GROUPCONSISTING OF RUBBERY COPOLYMER OF BUTADINE AND STYRENE IN ADMIXTUREWITH VULCANIZING INGREDIENTS, RUBBERY COPOLYMER OF BUTADIENE ANDACRYLONITRILE IN ADMIXTURE WITH VULCANIZING INGREDIENTS, RUBBERYCOPOLYMER OF ISOPRENE AND STYRENE IN ADMIXTURE WITH VULCANIZINGINGREDIENTS, AND RUBBERY POLYMERIZED CHLOROPRENE, AND DISSOLVEDPARTIALLY CONDENSED RESIN OBTAINED BY THE PARTIAL CONDENSATION OF APOLYHYDRIC PHENOL HAVING HYDROXYL GROUPS IN THE 1- AND 3-POSITIONS ANDAN ALDEHYDE AND CAPABLE OF SETTING IN THE AQUEOUS CONDITION TO A FRIABLESOLID GEL AND CAPABLE OF BENG CONVERTED UPON REMOVAL OF WATER TO ASUBSTANTIALLY INFUSIBLE, SUBSTANTIALLY INSOLUBLE STATE, SAID MIXTURECONTAINING SAID RUBBERY POLYMER AND SAID RESIN IN SUCH RELATIVEPROPORTIONS THAT THE POLYHYDRIC PHENOL CONTENT OF SAID RESINRANGES FROM3.8 TO 16.8% BY WEIGHT BASED ON THE WEIGHT OF SAID RUBBERY POLYMER ANDCONTAINING AT LEAST 30% BY WEIGHT OF SAID RUBBERY POLYMER AND SAIDRESIN.